Upon receiving a VFR on Top clearance, what altitude must a pilot maintain?

When a pilot receives a VFR on Top clearance, they are being instructed to operate under visual flight rules while remaining above a cloud layer or other obstructions. The requirement to maintain any VFR altitude above the Minimum Enroute Altitude (MEA) ensures that the aircraft remains within safe operational limits while also allowing the pilot to navigate visually.

The MEA is the lowest altitude that guarantees navigation signal coverage and obstacle clearance on a given airway segment, which is critical for safe flight. By specifying that the altitude must be above the MEA, it ensures that the aircraft is not only compliant with air traffic control instructions but is also flying safely by avoiding obstacles and ensuring coverage from navigational aids.

While pilots are allowed a degree of flexibility in terms of altitude when operating VFR on Top, they must still adhere to the regulatory requirements regarding minimum safe altitudes, which is why this option is the correct one.